1. Field of the Invention
The present invention relates to fountain solutions for use in lithographic printing operations and, more particularly, to a non-aqueous fountain solution.
2. Description of the Related Art
Offset printing, or lithography, is a printing technique in which the image to be printed is fixed on a generally flat plate. The lithographic process is based on the principal that oil and water do not mix. Using this principal, the plate is constructed so that the image areas are ink receptive and lipophilic or water repellant and the non-image areas are hydrophilic or water receptive and ink repellant. Fountain solutions, also referred to as dampening solutions, are the agents used in lithography to wet the non-image area of the plate and repel the ink from such non-image areas.
Numerous patented and unpatented fountain solutions have been developed over the past several years. By far, the vast majority of such prior art fountain solutions are aqueous or liquid based. U.S. Pat. Nos. 5,279,648, 5,268,025, 5,336,302, 5,382,298, 4,865,646 and 4,604,952 exemplify the state of the prior art liquid based fountain solution.
Although somewhat useful for their intended purpose, the prior art aqueous fountain solutions have been found to have many inherent deficiencies. Many of these solutions use alcohol, typically isopropyl alcohol at a level of 10-15 percent, as an additive to fountain solutions. The alcohol reduces the surface tension of the aqueous fountain solution and acts as a wetting agent, viscosity modifier, emulsification aid and anti-foam agent. However, because of its volatile organic compound (VOC) characteristic, and resultant health and environmental effects, the use of alcohol is undesirable. Moreover, alcohol is an added cost and tends to reduce the quality of the printed material. Additionally, the aqueous solutions cause the containers holding such solutions to be heavy and cumbersome, resulting in significant storage, handling and freight costs. Moreover, the aqueous nature of these solutions increases the potential of environmental contamination following spillages and exposure to potentially harmful vapors from VOCs during manufacture and use of the solutions. Also, even after the aqueous solution has been consumed, disposal of the empty containers may pose environmental and health hazards.
In view of such health hazards, more recent aqueous fountain solutions, such as those disclosed in U.S. Pat. Nos. 5,279,648, 5,268,025, 5,336,302 and 4,865,646, have been developed without alcohol. However, many of these non-alcohol, aqueous fountain solutions employ other VOCs or chemicals considered to be harmful, such as ethylene glycol monobutyl ether, some of which are now regulated or prohibited by federal or state laws due to their inherent environmental and health hazards. Furthermore, the use of the alternative surface active agents often result in further undesirable properties, such as foaming and ink over emulsification. Additionally, these non-alcohol aqueous solutions still include the deficiencies inherent in aqueous solutions discussed above.
Notwithstanding the above identified problems inherent in aqueous fountain solutions, fountain solutions commercially available today are still predominately aqueous and, consequently, still include the inherent deficiencies discussed above. A few non-aqueous solutions, such as those disclosed in U.S. Pat. Nos. 4,234,443 and 4,374,036, have been developed, but have generally not been commercially successful. U.S. Pat. No. 4,234,443 discloses an alkaline fountain solution, which the inventor, Canale, claims addresses problems with image deterioration and ink-receptiveness of background areas associated with acidic solutions, thereby improving the transference of the ink to the paper on which the image is being printed. However, in U.S. Pat. No. 4,374,036, Canale acknowledges that alkaline solutions, such as those disclosed in his earlier patent, also interfere with the transference of the ink to the paper and, consequently, discloses a neutral solution to address such problem.
Although the non-aqueous fountain solutions disclosed in U.S. Pat. Nos. 4,234,443 and 4,374,036 eliminate some of the problems discussed above inherent in aqueous solutions, they are designed for generally lower quality web fed type printing, such as newsprint, and are not well-suited for use with the modern high speed printing presses used today in commercial multi-color printing. Specifically, the neutral and alkaline solutions are not capable of rendering the properties required for use with today's newer, faster equipment for a variety of reasons. First, the increased speed and improved performance of today's newer equipment necessitates a corresponding speed and performance improvement of its collateral products, such as the cleansing and wetting capabilities of fountain solutions. The neutral and alkaline solutions do not cleanse the plate fast and effective enough to accommodate the increasing speeds of today's presses. In fact, some of today's newer systems will not function correctly at a pH greater than 4.0. Second, although alkaline based solutions were suitable for use with older generation inks based on mineral oils, they are generally incompatible with newer generation inks comprising vegetable oils, such as soy, linseed and rapeseed. When a vegetable oil and alkali are mixed, the resultant chemical reaction produces a water soluble soap, which adversely effects the equipment's performance and resultant quality of the printed material.
Accordingly, there is a need in the art for a non-aqueous, acid-based fountain solution composition capable of achieving the speed and performance criteria required by today's newer high speed multi-color lithographic printing systems. Any such composition should include a surfactant system capable of attaining dynamic surface tension measurements similar to those generated by aqueous solutions having isopropyl alcohol, without foaming, ink over-emulsification and other undesirable properties, and be capable of reducing the quantity of alcohol required for optimum performance. The present invention is particularly suited to overcome those problems which remain in the art in a manner not previously known.